Please help me with this problem..

Find two rational expressions that have the difference of 2-n/n-4

Which of these people has balanced their checkbook correctly? oa. gary: the balance in his check register is $500 and the balance in his bank statement is $500. b. gail: the balance in her check register is $400 and the balance in her bank statement is $500. c. gavin: the balance in his check register is $500 and the balance in his bank statement is $510.

What is the number 321,000,000 in scientific notation? also what is the number? ?